The invention relates to implants for humans or animals. The implants at least partly create positive-fit connections to human or animal tissue parts, particularly skeletal parts, wherein the implants help connect tissue parts together, or help connect tissue parts to means supporting or replacing tissue parts, or to other therapeutic auxiliary devices. The invention further relates to devices and methods for implanting implants into humans or animals.
Known implants for creating connections to skeletal parts (bones) include screws, pins, agraffes etc., which are used for connecting bones to bones, or bones to artificial, carrying, stabilizing, or supporting parts, or to parts replacing skeletal parts (stabilization or fixation plates, sutures, wires, artificial joint elements, artificial teeth, etc.). Such connection elements for implantation consist for example of metal or plastic, including resorbable plastic. After healing, the connection elements are removed by a further operation or they are left in the body where they are possibly gradually decomposed and replaced by vital tissue.
For stabilizing a bone fracture, a fixation plate with suitable holes is fixed in the region of the fracture using screws as mentioned above. Plate and screws may consist of metal (e.g. stainless steel or titanium). The screws are self-cutting and are rotated into threadless openings in the bone, or they are screwed into pre-drilled threaded openings. Pins and agraffes are knocked into previously created openings for similar purposes. Connections created in the foregoing manner are usually based on frictional engagement, possibly on positive fit.
In all cases, large forces (torsional forces and impact forces) are to be applied on implantation, and possibly also on removal. This often means that the implants need to have a higher mechanical stability for implantation and removal, than for the load which they are to bear when implanted. In particular, for implants of resorbable plastic, which have a significantly lower mechanical strength than metal, this increased requirement for mechanical stability requires the implants to have relatively large cross sections, and thus, for implantation, undesirably large openings need to be created in the vital tissue.
Implantation of the named connection elements may also generate considerable quantities of heat and therewith impair the surrounding tissue, in particular due to the friction generated when producing a frictional engagement. This applies in particular to the cutting of threads, the screwing-in of self-cutting screws and the knocking-in of implants without prior drilling.
It is known also to use curable, plastic materials (e.g. particular cements on a hydraulic or polymer base) for creating connections of the mentioned type. Such materials are pressed from the outside between implant and vital tissue, or into tissue defects in a highly viscous condition, and are cured in situ. Positive-fit connections can be created using such material, if the openings into which the material is pressed comprise suitable undercuts.
It is the object of the invention to provide implants for creating positive-fit connections to tissue parts (in particular to bone parts, cartilage parts, tendon parts, ligament parts, but also to parts of other tissues), wherein the implants are able to be implanted in a simple, quick manner, with small forces, and wherein the implants are able to provide very stable connections immediately after implantation (primary stability). Furthermore, it is desired that the implants create fewer problems with regard to the generation of heat and formation of stress concentrations than is the case with at least some of the known implants, and that the volume of foreign material to be implanted is reduced. It is a further object of the invention to provide a device and a method for implanting the implants.